Table of Content

20 November 2017, Volume 46 Issue 11

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A New Method to Solving AR Model Parameters Considering Random Errors of Design Matrix

YAO Yibin, XIONG Zhaohui, ZHANG Bao, ZHANG Liang, KONG Jian

2017, 46(11):  1795-1801.  doi:10.11947/j.AGCS.2017.20170004

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The ordinary least square method could not solve the problem that the error exist both in design matrix and observation vector while compute parameter values of AR model. In this article, a new method is proposed which consider the random errors of design matrix. The source of design matrix and observation vector is same and the amount of parameters contain error can be equal by introducing virtual observation. Then, this problem could be solved under the framework of normal least square by equivalence transformation of observation equation. The result of this new method is superior to SVD method and normal least square method by simulation date and observation data which verify the feasibility and effectiveness of this method.

The Spherical Cap Harmonic Analysis Modeling Method Based on Disturbing Gravity Gradients

WANG Yi, JIANG Xiaodian

2017, 46(11):  1802-1811.  doi:10.11947/j.AGCS.2017.20160412

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It is deduced that the non-singular computational formulae of the disturbing gravity gradients based on spherical cap harmonic analysis theory.On the basis of the Tikhonov regularization method,the spherical cap harmonic model of local gravity field is calculated using GOCE satellite real surveying data.It is shown that the short wavelength information of local gravity field can be recovered from the disturbing gravity gradient data using spherical cap harmonic analysis method,and the difference with the GO_CONS_GCF_2_DIR_R5 model is at ±0.3×10^-5 m/s².

Analysis about Parameters Selection Strategy of ECOM Solar Radiation Pressure Model for BeiDou Satellites

MAO Yue, SONG Xiaoyong, JIA Xiaolin, RUAN Rengui

2017, 46(11):  1812-1821.  doi:10.11947/j.AGCS.2017.20160485

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In this paper,the variations of ECOM solar radiation pressure model parameters were analyzed for BeiDou satellites through orbit fitting using 3 years precise ephemeris data. The ECOM parameter selection strategies for the three types of BeiDou satellites were confirmed. Based on the satellite attitude control modes,satellite illumination was theoretically analyzed. We pointed out that solar panels are perpendicular illuminated,and then solar radiation pressure has the periodic component associated with the orbital period when satellite is at orbit-normal attitude control mode. Periodic parameters of D direction need to be added to enhance the ECOM 5 parameters. Orbit determination tests were carried out using MGEX global network data. Tests prove that using ECOM 7 parameters the orbit overlap accuracy improvement could reach up to 50%~80%.

Relative Pose Estimation and Accuracy Verification of Spherical Panoramic Image

XIE Donghai, ZHONG Ruofei, WU Yu, FU Han, HUANG Xiaochuan, SUN Zhenxing

2017, 46(11):  1822-1829.  doi:10.11947/j.AGCS.2017.20160645

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This paper improves the method of the traditional 5-point relative pose estimation algorithm, and proposes a relative pose estimation algorithm which is suitable for spherical panoramic images. The algorithm firstly computes the essential matrix, then decomposes the essential matrix to obtain the rotation matrix and the translation vector using SVD, and finally the reconstructed three-dimensional points are used to eliminate the error solution. The innovation of the algorithm lies the derivation of panorama epipolar formula and the use of the spherical distance from the point to the epipolar plane as the error term for the spherical panorama co-planarity function. The simulation experiment shows that when the random noise of the image feature points is within the range of pixel, the error of the three Euler angles is about 0.1°, and the error between the relative translational displacement and the simulated value is about 1.5°. The result of the experiment using the data obtained by the vehicle panorama camera and the POS shows that:the error of the roll angle and pitch angle can be within 0.2°, the error of the heading angle can be within 0.4°, and the error between the relative translational displacement and the POS can be within 2°. The result of our relative pose estimation algorithm is used to generate the spherical panoramic epipolar images, then we extract the key points between the spherical panoramic images and calculate the errors in the column direction. The result shows that the errors is less than 1 pixel.

On-orbit Radiometric Calibration Method of Spaceborne Multi-camera Mosaic Imaging Sensor

HAN Jie, XIE Yong

2017, 46(11):  1830-1840.  doi:10.11947/j.AGCS.2017.20170071

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As the core and foundation of quantitative remote sensing, the precision of on-orbit radiometric calibration of spaceborne sensor directly determines the quality of quantitative remote sensing production. However, the available radiometric calibration methods have been unable to achieve the absolute radiometric calibration of each camera and the relative radiometric correction among cameras simultaneously for multi-camera mosaic imaging sensor. Therefore,taking wide field of view(WFV)multispectral sensor equipped with GF-1 satellite as example,this research proposes an innovative on-orbit radiometric calibration method based on the modified radiometric block adjustment. First,the radiometric control points of each WFV camera are extracted using the traditional cross calibration method. Then the radiometric tie points of adjacent WFV cameras in the overlapping regions are obtained. At last,the integrate adjustment method is used to calculate the calibration coefficients of each WFV camera and the parameters of radiometric constraint equation considering the coupling relationship between the relative radiometric correction and the absolute radiometric calibration. The experimental results show the relative errors of the absolute radiometric calibration coefficients in each band are all less 9.34%. Meanwhile,the absolute radiometric calibration coefficients can realize relative radiometric correction among WFV cameras. The average absolute values of top of atmosphere (TOA) radiance differences in the overlapping region of adjacent cameras in each band are all less 1.63 W·m^-2·sr^-1·μm^-1.

A Spiral-based Construction of Adjacent Pixel Sets for Linear Spectral Unmixing

LIU Boyu, CHEN Jun, XING Huaqiao, WU Hao, ZHANG Jun

2017, 46(11):  1841-1849.  doi:10.11947/j.AGCS.2017.20170109

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The problem of spectral mixing in fragmented landscape prevents the potentiality of high temporal resolution image from land surface detail dynamic monitoring. The general way is unmixing the spectrum to components based on linear spectral mixing model,with the aid of neighborhood pixels and the least squares method. However,constructing the neighborhood pixel set by a window leads to the underdetermined problem in some areas. This paper analyses the cause of the problem,and introduces spiral to construct optimal neighborhood pixel set as a solution. Experiment on GlobeLand 30 shows that the spiral method has a good applicability for each land surface type. Compared with the traditional method,the overall accuracy can be enhanced by 2%,the accuracy of unmixed results can be improved by nearly one order of magnitude.

Reliable Line Matching Algorithm for Stereo Images with Topological Relationship

WANG Jingxue, ZHU Qing, WANG Weixi

2017, 46(11):  1850-1858.  doi:10.11947/j.AGCS.2017.20170162

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Because of the lack of relationships between matching line and adjacent lines in the process of individual line matching, and the weak reliability of the individual line descriptor facing on discontinue texture, this paper presents a reliable line matching algorithm for stereo images with topological relationship. The algorithm firstly generates grouped line pairs from lines extracted from the reference image and searching image according to the basic topological relationships such as distance and angle between the lines. Then it takes the grouped line pairs as matching primitives, and matches these grouped line pairs by using epipolar constraint, homography constraint, quadrant constraint and gray correlation constraint of irregular triangle in order. And finally, it resolves the corresponding line pairs into two pairs of corresponding individual lines, and obtains one to one matching results after the post-processing of integrating, fitting, and checking. This paper adopts digital aerial images and close-range images with typical texture features to deal with the parameter analysis and line matching, and the experiment results demonstrate that the proposed algorithm in this paper can obtain reliable line matching results.

Optimization Decomposition Method of Full-waveform LiDAR

WANG Binhui, SONG Shalei, GONG Wei, CHEN Zhenwei, LIN Xin, CHENG Xuewu, LI Faquan, SHI Shuo

2017, 46(11):  1859-1867.  doi:10.11947/j.AGCS.2017.20170045

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With the improvement of data storage capacity and data-processing capabilities,full waveform LiDAR develops rapidly and then from waveform data abundant information about the physical characteristics of the targets can be effectively retrieved through data processing. Waveform decomposition is therefore the key to full waveform LiDAR data processing. However,the number and initial parameters of the echo components are difficult to set in waveform decomposition. Conventional decomposition methods detect echo components by peak points or using the threshold method,which may ignore some overlapping components and show low accuracy. To this end,in this paper a novel method based on LM algorithm that takes into account both peak points and inflection points is adopted and it can extract the location,amplitude and FHWM of the echo components,proving it is a reliable and high accurate decomposition algorithm. To further demonstrate the advantages of the suggested method,waveform data measured by a full waveform LiDAR demonstration system and generated from simulation were both decomposed using the method. The results show that the suggested algorithm is efficient,promising and can effectively decompose adjacent echo components,then will improve the accuracy in the next phase of data processing.

Vegetation Height Inversion Method with Three-layer Model by Fusing the Ascending and Descending PolInSAR Data

SHEN Peng, WANG Changcheng, ZHU Jianjun, GAO Han, FU Haiqiang, XIE Qinghua, WANG Sai, HE Shuaishuai

2017, 46(11):  1868-1879.  doi:10.11947/j.AGCS.2017.20170122

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The acquisition of forest parameters can not only estimate the surface biomass and underlying topography,but also contribute to the study of global carbon cycle and global climate change.Vegetation parameter inversion algorithm with polarimetric interferometric SAR (PolInSAR) is generally based on the two-layer RVoG(random volume over ground) model.However,when the actual vegetation has three-layer structure of canopy,trunk layer and surface layer,the vegetation parameters inversion accuracy will decrease.As the vertical effective wave number difference between the near and far range in the case of airborne SAR system is large,it will bring the system error to the final inversion results.To solve these two problems,this paper proposes an algorithm of three-layer vegetation parameters inversion by fusing the ascending and descending PolInSAR data.The proposed method uses the three-layer RVoG model to correct scattering process of radar echo in vegetation.Then it combines the ascending and descending PolInSAR datasets to weaken the system errors; Finally,we use the non-linear iteration adjustment for tree height inversion.In order to validate the proposed algorithm,two ascending and two descending P-band full polarization SAR data acquired by ESAR airborne platform under the German space agency (DLR) BioSAR 2008 campaign are utilized and other three inversion strategies are used for comparison and analysis.The results prove the correctness of the three vegetation model,and the proposed method reduces the system error caused by the vertical effective wave number and improves the precision of tree height inversion.

Change Detection Method for High Resolution Remote Sensing Images Using Random Forest

FENG Wenqing, SUI Haigang, TU Jihui, SUN Kaimin, HUANG Weiming

2017, 46(11):  1880-1890.  doi:10.11947/j.AGCS.2017.20170074

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Studies based on object-based image analysis (OBIA) representing the paradigm shift in remote sensing image change detection (CD) have achieved remarkable progress in the last decade.Their aim has been developing more intelligent interpretation analysis methods in the future.The prediction effect and performance stability of random forest (RF),as a new kind of machine learning algorithm,are better than many single predictors and integrated forecasting method. This paper presents a novel RF OBIA method for high resolution remote sensing image CD that makes full use of the advantages of RF and OBIA. Firstly,the entropy rate segmentation algorithm is used to segment the image for the purpose of measuring the homogeneity of super-pixels. Then the optimal image segmentation result is obtained from the evaluation index of the optimal super-pixel number.Afterwards,the spectral features and Gabor features of each super-pixelareextracted and used as feature datasets for the training of RF model.On the basis of the initial pixel-level CD result,the changed and unchanged samples are automatically selected and used to build the classifier model in order to get the final object-level CD result.Experimental results on Quickbird,IKONOS and SPOT-5 multi-spectral images show that the proposed method out performs the compared methods in the accuracy of CD.

An Algorithm Creating Thumbnail for Web Map Services Based on Information Entropy and Trans-scale Similarity

CHENG Xiaoqiang, YANG Min, GUI Zhipeng, AI Tinghua, WU Huayi

2017, 46(11):  1891-1898.  doi:10.11947/j.AGCS.2017.20170080

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Thumbnail can greatly increase the efficiency of browsing pictures,videos and other image resources and improve the user experience prominently. Map service is a kind of graphic resource coupling spatial information and representation scale,its crafting,retrieval and management will not function well without the support of thumbnail. Sophisticated designed thumbnails bring users vivid first impressions and help users make efficient exploration. On the contrast,coarse thumbnail cause negative emotion and discourage users to explore the map service positively. Inspired by video summarization,key position and key scale of web map service were proposed. Meanwhile,corresponding quantitative measures and an automatic algorithm were drawn up and implemented. With the help of this algorithm,poor visual quality,lack of map information and low automation of current thumbnails was solved successfully. Information entropy was used to determine areas richer in content and tran-scale similarity was calculated to judge at which scale the appearance of the map service has changed drastically,and finally a series of static pictures were extracted which can represent the content of the map service. Experimental results show that this method produced medium-sized,content-rich and well-representative thumbnails which effectively reflect the content and appearance of map service.

A Hand-drawn Map Retrieval Method Based on Open Area Spatial Direction Relation

AN Xiaoya, LIU Pingzhi, JIN Cheng, XU Daozhu, WANG Feng

2017, 46(11):  1899-1909.  doi:10.11947/j.AGCS.2017.20170001

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To meet the needs of retrieving the geographic information intelligently,a hand-drawn map retrieval method based on open area spatial direction relation is proposed.Firstly,it is designed that a new type of open area spatial direction relation description model and calculation method based on the opening area between the hand-objects,which can be used to hand-drawn map retrieval,both can be adapted to accurately describe by open area,but also through the relaxation strategy to describe the fuzzy relationship.A hand-drawn map retrieval process based on open area spatial direction relation is proposed.The evaluation model,similarity calculation of spatial direction relation and R-tree spatial index are given.The experiment results show that the method can retrieve the top-ranking results effectively in a large scope map scene.

A Habitation Selection Method by Using Case-based Reasoning

XIE Limin, QIAN Haizhong, HE Haiwei, LIU Chuang, DUAN Peixiang

2017, 46(11):  1910-1918.  doi:10.11947/j.AGCS.2017.20170061

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Aiming at the problem that the experience of expert in small and medium scale maps is difficult to be expressed in the habitation selection, this paper puts forward a method based on KNN and case-based reasoning on the habitation selection. First of all, the experts selection result on the habitation as cases. Mining habitation property attribute of cases, attribute assignment and the normalization before construction of source database; then, the method of stepwise elimination is used to select the best attribute combination, and training data to determine the optimal K value of KNN algorithm; finally, combined CBR and KNN algorithm to match the new case with the source case library, and get decision result to guide the automatic selection of habitation. The experimental results show that the proposed method can reduce the selection intention of experts, and has better noise immunity. It achieved a good result in the automatic selection of areal habitation.

A Weighted Voronoi Diagram-based Retrieval Approach for Point-like Toponym Information

ZHANG Yu, WANG Qi, WU Wenzhou, SU Fenzhen

2017, 46(11):  1919-1926.  doi:10.11947/j.AGCS.2017.20170125

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Considering the fact that most of the place names in the gazetteer record the spatial information only in the form of center coordinates,which lacks the description of the specific spatial extent of the place name,one-sidedness and limitations exist in the toponym information retrieval. Based on the fully analysis of the place names,spatial attributes and spatial relations,the paper proposes a weighted Voronoi diagram-based retrieval approach for point-like toponym information,which considers the importance of different properties of the place names belonging to the same type in the information retrieval,and takes advantage of the weighted Voronoi diagram in the boundary approximation of the place. The approach constructed weighted Voronoi diagram based on the area properties of the same type place names,and approximated the spatial extent of the place. Then,spatial relation between two places could be described,and the spatial similarity was achieved by the given equations to calculate the similarities of the topological,directional and distance relationship. The approach was verified by approximating boundaries of administrative divisions and retrieving their information. The experiment results show that the approach can be better applied in the approximation of spatial extents and relations of place names,and the spatial similarity matching between query words and geographical information resources can be improved. Finally,the proposed approach is better than the traditional approaches.